These notes are intended to document the EIKONXS program running on the Intel iPSC/2 multicomputer at Daresbury Laboratory in 1989. The program, derived from PAMPA, EIKON and TANGO (Gaussorgues, Piacentini and Salin [1,2]) calculates cross sections for total and angular differential charge transfer and electronic excitation, orbital alignment and orientation parameters and radiative transitions during the collisions of ions and atoms. The treatment uses adiabatic and diabatic molecular wavefunctions with a common electron factor and classical trajectory. A formal derivation is given of some of the equations used in the program. This may serve as a concise introduction to the theory of molecular charge transfer.